Endoprostheses can be used to replace a missing biological structure, support a damaged biological structure, and/or enhance an existing biological structure. Frequently, only a temporary presence of the endoprosthesis in the body is necessary to fulfill the medical purpose. Surgical intervention to remove endoprostheses, however, can cause complications and may not even be possible. One approach for avoiding a permanent presence of all or part of an endoprosthesis is to form all or part of the endoprosthesis out of bioerodible material. The term “bioerodible” as used herein is understood as the sum of microbial procedures or processes solely caused by the presence of endoprosthesis within a body, which results in a gradual erosion of the structure formed of the bioerodible material.
At a specific time, the endoprosthesis, or at least the part of the endoprosthesis that includes the bioerodible material, loses its mechanical integrity. The erosion products are mainly absorbed by the body, although small residues can remain under certain conditions. A variety of different bioerodible polymers (both natural and synthetic) and bioerodible metals (particularly magnesium and iron) have been developed and are under consideration as candidate materials for particular types of endoprostheses. Many of these bioerodible materials, however, have significant drawbacks. These drawbacks include the erosion products, both in type and in rate of release, as well as the mechanical properties of the material.